In typical electrophotographic type reproduction machines, during the course of each operating cycle, latent electrostatic images of the subject matter being reproduced are generated on a moving recording member. This recording member typically comprises a layer of photoconductive insulating material on a conductive backing, is given a uniform electric charge over its surface and is then exposed to the subject matter to be reproduced, usually by conventional projection techniques. This exposure creates an electrostatic latent image on the coating on the recording member. Following exposure, the latent electrostatic images on the recording member are developed at a developing station through the use of a developer mixture. In electrophotographic type reproduction machines that use dry developers for developing electrostatic images, the typically employed developer mixture includes a toner material and a carrier material. The developed image is then transferred at a transfer station to a support material, such as a sheet of paper. Subsequently, the developed image is fixed by any suitable means to provide a permanent image or reproduction.
Conventionally, image forming devices, such as laser printers and facsimile machines, employ an exposure system, a photoreceptor and a developer. An electrostatic latent image is formed on the photoreceptor by exposing it to laser light and the latent image is subsequently developed into a visible toner powder image. The visible toner image is then transferred from the photoreceptor onto a physical medium, such as a sheet of paper. The photoreceptor is typically a portable drum having a photosensitive surface. Processing stations are sequentially disposed around the photoreceptor and are fixed in position with respect to each other and to the photoreceptor. Such processing stations generally include a charging station, an exposure station, a developing station and a transfer station.
The charging station imparts an electrical charge onto the photosensitive surface of the photoreceptor and typically includes a corona charging wire. The electrical charge enables the toner image to be formed on the photoreceptor. The exposure station stations forms an electrostatic latent image on the photosensitive surface of the photoreceptor through an imaging light source (laser beam). The developing station develops the latent image on the photosensitive surface of the photoreceptor into the visible toner image and typically includes a supply of tone, such as powder, and a developing roller that transfers the toner powder onto the photoreceptor. The transfer station transfers the visible toner powder from the photoreceptor to the paper sheet, generally by use of a transfer wire.
In addition, a fixing device is provided which fixes or stabilizes the visible image on the paper sheet and enables the paper sheet to be handled without destroying the image. The fixing device typically works on the principle of heat and pressure rollers. A residual toner removing device, such as a cleaning blade, is also provided for removing toner that remains on the photoreceptor after the toner image has been transferred to the paper sheet. A discharge of pre-exposure station, such as an erase light, may also be provided to remove any residual electrical charge on the photoreceptor after the image has been transferred to the paper sheet. The discharge station is typically positioned between the toner removing device and the corona charging station.
During the development of such images, the toner portion of the developer mixture is depleted. In order to maintain the requisite portion of toner, fresh toner must be resupplied periodically. The means for supplying fresh toner must operate smoothly and consistently and must be reliable as well as leak-free for an electrophotographic machine or the like to operate properly.
Various types of toner resupply systems are known to the prior art as, for example, the container or cartridge types shown by U.S. Pat. Nos. 3,337,072 (Del Vecchio et al.), 4,091,765 (Lowthorp et al.), 5,118,013 (Mutou et al.) and 5,235,389 (Kikuchi et al.). All four of these prior art arrangements teach a toner supply cartridge consisting of relatively rotatable inner and outer concentric cylinders, each with a toner dispensing opening or openings. The supply of fresh toner is held in the inner cylinder, and by rotating the inner cylinder relative to the outer cylinder, the discharge openings of each cylinder are brought into alignment thereby allowing for the dispensing of toner. To close the dispensing openings, the inner cylinder is again rotated relative to the outer cylinder such that the inner cylinder toner dispensing openings are closed by the inner surface of the outer cylinder.
One disadvantage of these concentric cylinder-type designs is that a deformation of either the inner or outer cylinder will make it impossible to achieve a desired smooth, rotational sliding motion between the outer surface of the inner cylinder and inner surface of the outer cylinder. Rather, such deformation will cause these portions of the cylinders to rub together. This interference between the cylinders will lead to abrading. As these portions of the cylinders become worn and damaged, the cylinders will no longer be able to rotate properly relative to each other thereby causing the improper dispensing of toner or lack thereof and/or leakage. Further, with the concentric cylinder design, large surface areas of the cylinders have the potential of interfering with each other due to deformation at any given time. The more surface contact between the cylinders, the greater the likelihood that a deformation in either cylinder will impede the proper functioning of the cartridge.
Similarly, U.S. Pat. No. 5,030,997 (Michlin et al.) teaches a toner supply and dispensing cartridge consisting of a cylinder having a plurality of toner supply ports spaced along its length and parallel to its longitudinal axis. Disposed within the interior of and extending the length of the cylinder is a multi-cup scoop, which rotates causing the dispensing of toner as the cylinder rotates. Optionally, a stationary sleeve may be disposed around the rotatable cylinder. The sleeve is provided with a plurality of openings corresponding to the location of the toner supply ports of the cylinder so that as the cylinder rotates, the ports periodically come into alignment with the openings thereby permitting the discharge of toner. The same problems encountered with the concentric cylinder-type designs wherein the cylinders rotate relative to one another would also be encountered in the design taught by Michlin et al. wherein only the inner cylinder rotates while the outer sleeve remains stationary.
U.S. Pat. No. 4,688,926 (Manno) teaches a reproduction machine having a rotatable toner supply cartridge. The toner supply cartridge consists of a hollow tube or cylinder having a plurality of toner discharge ports extending along its longitudinal axis and a means for controlling the timing and dumping of the toner from the toner discharge ports into a developer housing.
In one embodiment of the toner supply cartridge, the cylinder is provided with a plurality of spaced slot-like toner discharge ports in its surface. A rotatable, elongated toner dumping or ejecting rod is provided to control the timing and dumping of the toner from the toner discharge ports into the developer housing. This rotatable ejecting rod consists of a series of flats or recesses and is held in tight contact with the exterior surface of the cylinder extending the length of the cylinder opposite the row of toner discharge ports. As the cylinder rotates so that the toner discharge ports face the developer housing, the ejecting rod is rapidly rotated from a position where the flats are facing the toner dispensing ports and picking up toner to a position where the flats are facing toward the interior of the developer station. As a result, the toner deposited on the flats is ejected into the developer housing.
In an alternative embodiment, the cylinder has a plurality of spaced circular discharge ports in its surface extending along its longitudinal axis and is provided with an elongated rigid strip-like slide plate. This slide plate has a series of toner discharge ports capable of mating with those of the cylinder and is sealably held in position on the exterior of the cylinder opposite the row of toner discharge ports. The reciprocal sliding movement of the slide plate, in a longitudinal direction along the exterior surface of the cylinder, causes the opening and closing of the toner discharge ports thereby controlling the dispensing of toner.
The problem with this type toner resupply cartridge, is that it is mechanically complex and somewhat cumbersome. This design contains several moving parts, which increases the opportunity for malfunction and necessitates careful quality control to protect against or minimize product failure. The added quality control needed can be overly time consuming as well as add to the expense of production.
Thus, it is desirable to provide a toner supply cartridge that is simply constructed from a minimum number of parts, easily operated, leak-free and operational with minimal cylinder degradation.
The invention disclosed herein has accomplished this by providing a toner supply cartridge having a single hollow cylinder fitted with an internal shutter member. The design allows for excellent slidability between the shutter member and the interior surface of the cylinder of the toner supply cartridge thereby providing smooth, reliable, consistent and leak-free operation of the toner supply cartridge.